1. Field of the Invention
The present invention relates to a transmission assembly, and more particularly relates to a transmission assembly for a roller blind that can hold a blind cloth of the roller blind on a desired height and can roll the blind cloth up automatically and easily.
2. Description of Related Art
Conventional shades or blinds are generally used in the building decoration, include pleated shades, honey combs, roman shades and roller blinds. The conventional roller blind usually has a transmission assembly, a blind cloth and a lift cord. The transmission assembly is mounted on a side of a window frame. The blind cloth is rolled around the transmission assembly. The lift cord is connected to the transmission assembly and can be pulled to control the expansion or retraction of the blind cloth via the transmission assembly. However, the lift cord is hanged down at a side of the conventional roller blind, and a child is easily tied by the conventional lift cord to cause accidents.
Therefore, a cordless transmission assembly of the conventional roller blind is provided and has a mounting frame, a torsional spring, a connecting cord, a lower bar and a blind cloth. The mounting frame is mounted securely on a side of a window frame. The torsional spring is mounted in the mounting frame and has two ends. One of the ends of the torsional spring is connected to the mounting frame. The connecting cord is connected to the other end of the torsional spring and has a lower end. The lower bar is connected to the lower end of the connecting cord opposite to the torsional spring. The blind cloth is mounted between the mounting frame and the lower bar. The torque force of the torsional spring is equal to the weight of the blind cloth and the lower bar to hold the blind cloth at a desired height. Although the cordless conventional roller blind has been provided to a hold the blind cloth in place, the conventional cordless transmission assembly cannot be rolled up easily and automatically especially when the conventional roller blind is set at a high position.
To overcome the shortcomings, the present invention provides a transmission assembly for a roller blind to mitigate or obviate the aforementioned problems.